The prevalence of obesity (BMI≥30 kg/m2) continues to be a health concern for adults, children and adolescents in the United States. Data from the NHANES survey shows that among adult men the prevalence of obesity increased from 31.1% in 2003-04 to 32.2% in 2007-08, a small but not statistically significant change. Among adult women, the prevalence of obesity increased from 33.2% in 2003-04 to 35.5% in 2007-08, again a small but not significant change (Ogden et al. Gastroenterology 2007; 132 (6):2087-2102; Flegal et al. JAMA 2009; 303 (3):235-241). In Europe, the prevalence of obesity has increased by 10 to 38%, depending on the country, over the last 10 years (World Health Organization 2003; Factsheet #894). Type 2 diabetes (T2D), often associated with excess weight, affects more than 3% of the world's population, or more than 220 million people (World Health Organization 2009; Factsheet 312). This figure is projected to rise to 300 million by 2025 (Zimmet et al. Nature 2001; 414:782-787).
Recent epidemiological studies have shown the beneficial effect of coffee in terms of prevention of T2D, also known as fatty diabetes. T2D is a dysfunction of the mechanism that regulates blood glucose concentration, resulting in insulin resistance. This insulin resistance is expressed as abnormal and prolonged hyperglycemia. Before resulting in T2D, this hyperglycemia consists of an excess of blood glucose which can metabolize into triglycerides, hence, causing weight gain.
Caffeine consumption of 5 mg/kg/day is known to have a role in insulin resistance (Graham et al. Can. J. Physiol. Pharmacol 2001; 79 (7):559-565). Because coffee is the primary dietary source of caffeine, a number of epidemiological studies have been conducted to assess the correlation between the coffee consumption of different Western and Asiatic populations and the risk of occurrence of T2D.
TABLE 1Summary of studies on the risk of type 2 diabetes as a function of coffee consumption.Origin ofNumber ofDailythe populationLength ofindividualsconsumptionDecreaseReferencesstudiedthe studymonitoredSexof coffeein risk %PR. M. Van Dam, 2002Holland10 years17,111Mixed≥7 cups50<0.0002A. Reunanen, 2003Finland 4 years19,518Mixed≥7 cups8notreportedJ. Tuomilehto, 2004Finland12 years14,629Mixed≥10 cups 61<0.001E. Salazar-Martinez,United22 years41,934Men≥6 cups54<0.0012004StatesE. Salazar-Martinez,United18 years84,276Women≥6 cups29<0.0012004StatesR M van Dam et al,United9.8 years 88,259Women≥4 cups47<0.00012006StatesH. Iso et al., 2006Japan 5 years17,413Men &≥3 cups42<0.027WomenM A Pereira et al., 2006United11 years28,812Women≥6 cups21<0.07StatesS. Bidel et al., 2008Finland12.5 years 21,826Men &≥7 cups36<0.0001WomenA O Odegaard et al.,Singapore5.7 years 36,908Men &≥4 cups30<0.022008WomenM. Kato et al., 2009Japan10 years24,826Men≥5 cups18<0.006M. Kato et al., 2009Japan10 years31,000Women≥5 cups60<0.001S. van Dieren et al.,Holland10 years38,176Men &≥6 cups7<0.042009WomenD S Sartorelli et al.,France11 years69,532Women≥3 cups27<0.0012010
Numerous epidemiological studies, mainly published between 2002 and 2010, have demonstrated that coffee consumption of between 3 and 10 cups per day decreases the risk of developing T2D. Table 1 summarizes studies conducted in populations of greater than 10,000 people, totaling 534,220 people in six countries. The ground-breaking study was reported by van Dam et al. (The Lancet, 2002; 360:1477-1478) showing the influence of higher or lower coffee consumption on health. After monitoring 17,111 Dutch people between 30 and 60 years old for 7 years, they clearly established a positive correlation between coffee consumption and a decrease in the risk of T2D. Participants drinking 7 cups of coffee or more per day were half as likely (P=0.0002) than participants drinking 2 cups of coffee or less per day to develop T2D. Therefore, there is a link between high coffee consumption and a decrease in the risk of T2D.
Naismith et al. (Nutr. Metabol. 1970; 12:144-151) studied the effect of coffee consumption on the blood sugar concentration. Their study, carried out on twenty healthy volunteers, concluded that certain compounds, other than caffeine, significantly reduce fasting blood sugar levels. This was also suggested by Isogawa et al. (The Lancet, February 2003; 361: 702-704). They converted the number of cups consumed into the quantity of caffeine ingested and showed that, despite the tendency to decrease the prevalence of fasting hyperglycemia, the consumption of caffeine alone had no notable effect (p=0.012). This study shows that the risk of fasting hyperglycemia is clearly lower in people consuming coffee, compared with its prevalence in tea drinkers, whatever type of preparation—green tea, fermented tea or oolong tea. No significant correlation has been established between the prevalence of fasting hyperglycemia and the consumption of tea, whether in terms of frequency of consumption or quantity of caffeine ingested. Salazar-Martinez (Ann Intern Med. 2004 Jan. 6; 140 (1):1-8) concluded that caffeine is not the active substance decreasing the risk of T2D. Indeed, a net decrease in the risk of T2D occurs for consumers of more than 6 cups of coffee per day. The investigators therefore concluded that molecules contained in coffee, but not caffeine alone, have a beneficial effect in terms preventing fasting hyperglycemia.
While caffeine is not the active substance that prevents blood sugar disorders, the various authors of the epidemiological studies mentioned in Table 1 suggest or agree that chlorogenic acids (CGA) do play a highly influential role in this. Current scientific consensus attributes the protective effect of chlorogenic acids to their capacity to regulate postprandial blood sugar concentration, inhibit the intestinal absorption of glucose, improve glucose tolerance, and, to a lesser extent, modulate serum lipid concentrations.
Chlorogenic acids (CGA) are a family of esters formed between certain hydroxycinnamic acids (i.e. caffeic and ferulic acids) and (−)-quinic acid. Green (or raw) coffee is a major source of CGA in nature (5-12 g/100 g) (Farah et al. Braz J Plant Physiol. 365 2006; 18:23-36). The major CGA in green coffee are 3-, 4- and 5-caffeoylquinic acids (3-, 4- and 5-CQA), 3,4-, 3,5- and 4,5-dicaffeoylquinic acids (3,4-, 3,5-, and 4,5-diCQA); 3-, 4- and 5-feruloylquinic acids (3-, 4- and 5-FQA) and 3-, 4- and 5-p-coumaroylqunic acids (3-, 4-, and 5-p-CoQA). Caffeoylferuloylquinic acids (CFQA) are minor CGA compounds also found in green coffee, especially in Coffea robusta species. Very small amounts of CGA lactones formed by heating during primary processing may also be observed (Farah et al. Braz J Plant Physiol. 2006; 18:23-36.—Farah et al. J Agric Food Chem. 2005; 53:1505-13).
Coffee berries, which contain the coffee bean, are produced by several species of small evergreen plants of the genus Coffea. The two most commonly grown species are Coffea robusta (also known as Coffea canephora) and Coffea arabica. These are cultivated in Latin America, Southeast Asia, and Africa. Concentrations on total chlorogenic acids (tCGA) are different in the two species. In general, tCGA concentration is higher in Coffea robusta than in Coffea arabica. Table 2 summarizes the content of FQA, CQA, and tCGA in the two coffee species before roasting.
TABLE 2Content of FQA, CQA, and tCGA in the Coffea arabica andCoffea robustaCoffea arabicaCoffea robustag/kgg/kgPhenolic acidsSantosSao PauloGhanaUgandaFeruloylquinic2.3-3.3  0-2.111.6-12.05.4-6.8acids (FQA)Caffeoylquinic60.8-62.656.2-58.279.2-84.377.1-80.9acids (CQA)Total chlorogenic64.2-64.856.5-59.192.6-94.783.9-86.6acids (tCGA)Clifford MN and Wright J, 1976
The torrefaction process has the aim of developing the coffee aroma. The traditional roasting method lasts between 15 and 23 minutes depending on the machinery. The coffee beans are gradually heated while being constantly tossed about. At about 100° C., the beans go yellowish and lose a good proportion of their water by evaporation. Towards 150° C., the beans that have become light brown begin to give off an aroma. Between about 200 and 250° C., the beans become a mahogany brown color. If the torrefaction is continued (230° C.), the bean becomes quite black. This change of color is known as the Stucker reaction. Under the effect of heat, certain constituents disappear; others combine with each other to form complex products. In the first 10 minutes, caramelization of sugars occurs from 160° C.: this is known as Maillard's reaction. At the end of about 10 minutes (200° C.), this reaction causes the first 4 aromas to arise from aroma precursor acids. These aromas are destroyed by possible carbonization. After 10 minutes, the bean will have lost most of its water by evaporation. The sugars and tannins gradually disappear. During the torrefaction process, the total chlorogenic acids are partially destroyed. Table 3 shows the destruction of chlorogenic acids as a consequence of the torrefaction process of the coffee. Therefore, it is desirable to avoid the roasting process in order to preserve a high content of chlorogenic acids in the coffee beans.
TABLE 3Effects of the torrefaction process over the total chlorogenic acids(tCGA) in the green coffee.TotalTorrefaction (205° C.)Green coffeechlorogenicSoftStrongReally strongbeansacids (tCGA)(7 min)Mild(13 min)(19 min)Coffea Arabica57.623.819.87.12.2(Guatemala)Coffea robusta68.230.217.85.21.4(Uganda)Trugo and Macrae, 1984
Studies managed by the NAT'Life Division of Naturex and INRA (National Institute of Agronomic Research) allowed to clarify chlorogenic acids absorption thanks to in situ stomach infusion, intestinal perfusion models and nutritional intervention experiment in rats. Different absorption sites and different metabolites were identified. The results showed that about 30% of chlorogenic acids are absorbed from the stomach and the small intestine, the other part reaching the colon (FIG. 1). From the stomach, the absorption does not induce modifications in the CGA structures. The absorption in the stomach represents about 16% of the total ingested. From the small intestine and the colon, most of the chlorogenic acids ingested are hydrolysed into caffeic and quinic acids. In the small intestine, chlorogenic acids are hydrolysed by enterocytes. The caffeic acid next liberated is O-methylated. After that, caffeic and (iso)ferulic acids go to the blood and can be metabolized in the tissues. In the colon, chlorogenic acids are hydrolyzed by the microflora. Quinic and caffeic acids are thus released, directly absorbed and metabolized by enterocytes, metabolized by the intestinal flora, absorbed and metabolized again by colonocytes and finally excreted in the feces.
It has been demonstrated that tCGA regulates glycemia by inhibiting glucose-6-phosphatase (Glc-6-Pase) system activity. Glc-6-Pase plays an important role in the homeostatic control of blood sugar concentration. This enzyme system, only present in the liver, is in fact responsible for the conversion of glucose-6-phosphate into glucose which is then capable of passing into the general circulation. Inhibition of hepatic Glc-6-Pase causes a reduction in the hepatic production of glucose and consequently decreases abnormally high levels of glucose in the blood.
Recent discoveries have shown that 5-caffeoylquinic acid (5-CQA) inhibits the activity of Glc-6-Pase in a specific way, in particular the activity of its Glc-6-Pase translocase 1 unit (T1) (McCarty. Med Hypotheses. 2001 March; 56 (3): 286-289). In vitro and in vivo studies carried out with 5-CQA, the main polyphenol in coffee, showed that this phenolic acid is able to modulate glucose metabolism (Welsch et al. J. Nutr., 1989. 119 (11):1698-1704.—Anion et al. Arch Biochem Biophys, 1997. 339 (2):315-22.—Herling et al. Am J Physiol, 1998. 274 (6 Pt 1): p. G1087-93.—Hsu et al. Planta Med, 2000. 66 (3): p. 228-30.—Andrade-Cetto et al. J Ethnopharmacol, 2001. 78 (2-3): p. 145-9.—Rodriguez de Sotillo et al. J Nutr Biochem, 2002. 13 (12): p. 717-726.—Johnston et al. Am J Clin Nutr, 2003. 78 (4): p. 728-33). More particularly, it was shown that 5-CQA inhibits Glc-6-Pase in intact rat microsomes while no effect was shown in fully disrupted microsomes. However, there is no evidence for the inhibition of Glc-6-Pase by other CGAs nor by green coffee extract.
Blum et al. (Nutrafoods 2007; 6 (3):13-17.) conducted a study in order to determine the hypoglycaemic effect of a green coffee extract (Svetol® green coffee extract, NATUREX) in humans. The aim of the clinical trial was to determine if the green coffee extract could decrease glycemia in the postprandial state in humans. Fifteen healthy women (18-70 y) participated in the study. All participants were used as their own control and were submitted to an oral glucose tolerance test before and after supplementation of the green coffee extract. The supplementation consisted of 600 mg of green coffee extract daily during forty days, divided in three doses of 200 mg each before the meals. Results indicated a significant decrease (147±9.3 vs 133±8.7 mg/dL; p<0.05) in post-load glycemia compared to the one obtained before supplementation (FIG. 2). Moreover at the end of the study, a weight loss of around 1.5 kg was noted. In conclusion, these preliminary results suggest that green coffee extract is able to modulate glucose metabolism and that this modulation could have an effect on weight management.
In another clinical trial, Deallalibera et al. (Phytothérapie expérimentale 2006 November; 4 (4):194-197) studied the effect of a green coffee extract (Svetol® green coffee extract, NATUREX) on body weight loss in humans. Fifty overweight volunteers (BMI>25 kg/m2) were randomized in two groups, control group (n=20) receiving placebo, and treated group (n=30) receiving the green coffee extract (Svetol® green coffee extract, NATUREX) with bland low calorie diet. Each volunteer took one capsule of the 200 mg of green coffee extract twice a day with the main meal, for 60 days. Changes in Muscle Mass/Fat Mass ratio (MM/FM), body weight, body mass index (BMI), and self evaluation of physical aspects were recorded at baseline and at the end of the study. After 60 days, the MM/FM ratio was increased statistically in the green coffee group compared to the placebo: 4.1±0.7% vs. 1.6±0.6% respectively (P<0.01). Moreover, a significant reduction in weight of 4.97±0.32 kg (5.7%), as well as in the BMI (−1.7 kg/m2), were observed in the green coffee extract compared to the placebo (P<0.001). The significant increase of MM/FM ratio and decrease of weight and BMI showed that the green coffee extract (Svetol® green coffee extract, NATUREX) is able to exacerbate effect of a bland low calorie diets on volunteers who are overweight. This effect could be explained by increasing the consumption of fatty deposits and by preventing them from being accumulated.